1. Field of the Invention
This invention belongs to the technical field of confinement or inert storage of polluting and toxic materials. The invention particularly refers to a process for the ultimate confinement of solid materials which may be in powder form or not, such as ultimate wastes, in order to avoid any danger for the environment. Further, the invention is related to shaped bodies as obtained by the process of the invention.
Numerous are the wastes and residues of our civilisation which can no longer simply be disposed of in pouring them on waste dumping grounds since their lixiviation by rain water and snow will contaminate the soil and the groundwater. Heavy metals such as zinc, copper, mercury, cadmium, nickel, lead and so on which can be found in numerous waste solids, especially in residual ashes of waste and garbage incineration plants, constitute a major risk. These metals, generally in the form of oxides, are enriched in the ashes and are particularly sensitive to lixiviation.
It is therefore nowadays necessary to stabilize these wastes by confinement with materials that must remain stable.
2. Description of the Prior Art
Until now, a method which is well established and currently used at a great scale is the stabilization of solid wastes, preferably ultimate wastes which cannot further be reduced in volume and in weight, by concrete confinement. The wastes are in principle blended with a concrete containing hydraulic binder, blocks are manufactured from the mixture to which water was added, the blocks are left for hardening, and the hardened blocks are finally stored at a safe place on a dumping ground under supervision.
However, it is of course not possible to store all these blocks thus manufactured in caverns where they are protected against meteorological precipitations, especially rain water. Concrete blocks are not inert against leaching or lixiviation brought about by these precipitations; the hardened concrete being a basic medium, it is attacked by water that contains acid substances such as atmospheric carbon dioxide and sometimes sulfurous, sulfuric, nitrous and nitric acids.
It has already been necessary to establish standards defining maximum metal concentrations in the lixiviated liquors which occur in an open air dumping ground. Furthermore, the maximum concentration of certain components, before all heavy metals, of the wastes to be confined in concrete blocks had to be limited. It follows that part or the wastes, namely those which contain more heavy metals than allowed, can no longer be confined normally but must be diluted in a certain manner before being contained and stabilized in the concrete.
Therefore, other possibilities for the confining treatment of wastes have been searched, and the stabilization of the residues by heat setting materials has been considered, see Environnement et Technique 127, 45 (June 1993). Depending on the physical state of solid, liquid or gas of the ultimate wastes to be stabilized, the confinement methods comprise coating, encapsulating and captivating techniques. The final objective of such methods is to contain and to isolate all these materials in a form that is permanently stable and that does not release toxic or dangerous substances.
For example, German Patent Application No. DE-A1-3,603,080 discloses a method for the manufacture of waste material blocks wherein shaped, artificial stone like bodies are first made from binders such as concrete, water and aggregates, and the wastes are then transferred into hollow boxes made from the shaped bodies. As a variant, the wastes are blended into the mixture of concrete, aggregate and water. Of course, this method shows the drawbacks of all concrete confinements even if the hollow boxes are lined with rubber or plastics sheets; this measure means an additional, expensive step, and there is no security of a permanent tightness of this liner.
The use of phenolics for the confinement of wastes has not yet become known so far.